Nicene and Ante-Nicene Fathers, Ser. II, Vol. III:Life and Works of Rufinus with Jerome's Apology Against Rufinus.: Section 4. I Believe in God the Father Almighty

The Eastern Churches almost universally deliver the article thus, “I believe in One God the Father Almighty;” and again in the next article, where we say, “And in Christ Jesus, His only Son, our Lord,” they deliver it., “And in One (Lord) our Lord Jesus Christ, His only Son;” confessing, that is, “one God,” and “one Lord,” in accordance with the authority of the Apostle Paul. But we shall return to this by-and-by. For the present, let us turn our attention to the words, “In God the Father Almighty.”

“God,” so far as the human mind can form an idea, is the name of that nature p. 544or substance which is above all things. “Father” is a word expressive of a secret and ineffable mystery. When you hear the word “God,” you must understand thereby a substance without beginning, without end, simple, uncompounded, invisible, incorporeal, ineffable, inappreciable, which has in it nothing which has been either added or created. For He is without cause who is absolutely the cause of all things. When you hear the word “Father,” you must understand by this the Father of a Son, which Son is the image of the aforesaid substance. For as no one is called “Lord” unless he have a possession or a servant whose lord he is, and as no one is called “master” unless he have a disciple, so no one can possibly be called “father” unless he have a son. This very name of “Father,” therefore, shews plainly that, together with the Father there subsists a Son also.

But I would not have you discuss how God the Father begat the Son, nor intrude too curiously into the profound mystery, lest haply, by prying too eagerly into the brightness of light inaccessible, you should lose the faint glimpse which, by the gift of God, has been vouchsafed to mortals. Or, if you suppose that this is a subject to be investigated with all possible scrutiny, first propose to yourself questions which concern ourselves, and then, if you are able to deal satisfactorily with them, speed on from earthly things to heavenly, from visible to invisible. Determine first, if you can, how the mind, which is within you, generates a word, and what is the spirit of the memory which is in it; and how these, though diverse in reality and in operation, are yet one in substance or nature; and though they proceed from the mind, yet are never separated from it. And if these, though they are in us and in the substance of our own soul, yet seem to be hidden from us in proportion as they are invisible to our bodily sight, let us take for our enquiry things which are more open to view. How does a spring generate a river from itself? By what spirit is it borne into a rapidly flowing stream? How happens it that, while the river and the spring are one and inseparable, yet neither can the river be understood to be, or can be called, the spring, nor the spring the river, and yet he who has seen the river has seen the spring also? Exercise yourself first in explaining these, and explain, if you are able, things which you have under your hands; and then you may come to loftier matters. Do not think, however, that I would have you ascend all at once from the earth above the heavens: I would first, with your leave, draw your attention to this firmament which our eyes behold, and ask you to explain, if you can, the nature of this visible luminary,—how that celestial fire generates from itself the brightness of light, how it also produces heat; and though these are three in reality, how they are yet one in substance. And if you are capable of investigating each of these, even then you must acknowledge that the mystery of the Divine generation is by so much the more diverse and the more transcendent as the Creator is more powerful than the creatures, as the artificer is more excellent than his work, as He who ever is more noble than that which had its beginning out of nothing.

That God then is the Father of His only Son our Lord is to be believed, not discussed; for it is not lawful for a servant to dispute about the nativity of his lord. The Father hath borne witness from heaven, saying, 3259
“This is My beloved Son, in Whom I am well pleased: hear Him.” The Father saith that He is His Son and bids us hear Him. The Son saith, “He who seeth Me seeth the Father also,” 3260
and “I and the Father are one,” 3261
and “I came forth from God and am come into the world.” 3262
Where is the man who can thrust himself as a disputant between these words of Father and Son, who can divide the Godhead, separate its volition, break asunder the substance, cut the spirit in parts, and deny that what the Truth speaks is true? God then is a true Father as the Father of the Truth, not begetting extrinsically, but generating the Son from that which Himself is; that is, as the All-wise He generates Wisdom, as the Just Justice, as the Everlasting the Everlasting, as the Immortal Immortality, as the Invisible the Invisible; because He is Light, He generates Brightness, because He is Mind, He generates the Word.